This invention relates to prosthodontics and, more particularly, to a method of fabricating "adjustment-free" dentures using a jig especially adapted for use in carrying out such method.
Artificial dentures must be accurately reproduced and accurately conform to mouth conditions existing prior to any extractions. However, it has long been the feeling that a certain number of "adjustment visits" are always necessary when making a set of dentures for a patient. During such visits, the doctor sees to it that:
(1) the patient can wear the dentures satisfactorily for eating and talking;
(2) he has no "sore spots" to be relieved;
(3) the upper and lower teeth will fit together to provide the natural bite and follow the relative motion established by masticating motion of his jaw structure; and
(4) the act of swallowing will not be hampered by the dentures.
Adjustments are usually made a few times before the final delivery of a completely finished set of dentures. It would be desirable to eliminate such annoying and sometimes painful "adjustment visits" almost entirely.
Various dental procedures for fabricating artificial dentures are currently available, a typical one of which includes the following steps:
1. A set of wax bite blocks is made as negative impressions of the upper and lower gum arches, in order to form a set of wax models for denture bases.
2. Artificial teeth are then attached to the wax models.
3. The next operating step is to form a lower plaster block using a metallic container conventionally called "flask" and consisting of upper and lower sections and top and bottom closure members. For this operation, a mixture of plaster material and water, or soft plaster, is poured into the flask's lower section with the bottom closure member and, the wax model is then submerged in the mixture but not entirely, leaving only small foot portions thereof above the level of the mixture. The soft plaster solidifies, providing the lower plaster block.
4. The wax model provided in the lower plaster block is then coated with a separating material to facilitate separating the lower plaster block from an upper plaster block to be described later. The upper section of the flask is then attached to the lower section and is filled with soft plaster to the level that submerges the wax model entirely. The upper section of the flask is then firmly closed by the upper closure member using a suitable fastening means, and the entire flask is left for a certain period of time until the soft plaster solidifies.
5. After the soft plaster has solidified, the flask is placed in a hot water bath to melt the wax model in the plaster assembly. The flask is then taken out from the hot water bath and opened. It will be observed that the wax model no longer retains its original shape. With the wax washed away, the artificial teeth extend into a cavity formed in the plaster assembly that exactly conforms to the actual shape of the wax model.
6. A pasty synthetic resin compound which is prepared by pouring a monomer into a mixing jar, slowly adding a synthetic resin powder, and stirring continuously until it will thicken due to its own reaction, is poured into the cavity while still soft enough to run. The flask is then closed and placed into a hot water bath to cause the synthetic resin compound to cure or harden due to polymerization induced by the heat from the hot water.
7. After the flask is taken out from the hot water bath, the plaster assembly is carefully broken apart to provide a denture comprising the artificial teeth planted on the denture base formed of the synthetic resin compound.
FIG. 1a illustrates the conventional dental procedure just described for making artificial dentures. The lower plaster block 20 is shown to have the cavity which is formed by submerging the wax model (not shown) in the soft plaster which solidifies to provide the lower plaster block 20. Since the wax model carries artificial teeth 22 (only one of which is shown for brevity of illustration), the teeth have their tips extending into the plaster block. As described above, after the lower plaster block 20 is formed, the concave surface 24 of the lower plaster block is coated with a separating material so as to make it easier to open the flask for the subsequent operation of washing away the wax model.
The upper plaster block 26 is formed by pouring soft plaster into the upper section of the flask to the depth that entirely submerges the wax model. After solidifying of the soft plaster, the flask is opened to expose the wax model within the cavity defined by the recess or concave portion of the lower plaster block 20 and the convex portion of the upper plaster block 26. Thereafter, the wax model which has lost its original shape due to the heat from the hot water bath is washed away, as described above.
It will be noted that the practice of this conventional procedure using the metallic two-section flask inherently entails the formation of an interface between the upper and lower plaster blocks. This interface will tend to cause a serious problem that in the subsequent polymerization step the curing synthetic resin compound will penetrate into a narrow gap 29 between the contiguous surfaces of the upper and lower plaster blocks despite the use of a special press which firmly holds the flask throughout the curing and cooling cycle. When this occurs, the denture does not fit the prescription precisely, causing adjustment problems. Also, the press which is used to apply the high pressure to the flask's upper and lower sections to avoid displacement of these sections is quite costly.
Accordingly, it is the principal object of this invention to provide an improved method of fabricating comfortable and well-fitted dentures with a view to overcoming the deficiencies of the prior art.
It is another object of this invention to provide an improved method of fabricating artificial dentures without use of the conventional two-section flask which, when assembled, inherently creates a narrow gap between the contiguous surfaces of the upper and lower plaster blocks, into which the curing synthetic resin compound penetrates thereby causing adjustment problems.
It is still another object of this invention to provide an improved method of fabricating artificial dentures, which enables the use of a regular prosthetic press in place of an expensive heavy duty press conventionally used by the prior art method.
It is a further object of this invention to provide a jig especially adapted for use in carrying out the method of this invention.